Problem with port engine

[trooper10]

I have just recently purchased a 2003 320 DA with 6.2 L inboards.
While I was out for a ride the other day, I noticed my synch gauge started to bounce around and my port tach would jump around between 100 to 300 RPM. I could also feel and hear it in the engine. This would only occur when I was up on plane and running around 3600 RPM mark. I would then slow down to around 1000 RPM and everything would be fine. I would then get back up on plane and everything would be good for about 4-5 minutes and this would occur again. Everything else seemed fine, water temp, oil pressure, volt gauges. Anybody have any ideas what could be causing this? The local merc mechanic can't make it out to have a look until next week. Could this possibly just be a bad plug or plug wire?

 

[daveduchaj]

Could be fuel starved, have you replaced the filters?

 

[trooper10]

No I have not replaced the filters, not sure if they were replaced before I bought the boat. I had a similiar problem with my old boat and it was a bad plug wire. I am going to change out my plugs and see if that helps.

 

[Bill Z]

A small filter in the CArberator intake had the same issue part costs 1.60 labor was 40.00

 

[trooper10]

Thanks for all the input. It ended up being my fuel filter. I changed it and my water separator filter. Everything running good for now.